1. Field of the Invention
The present invention relates to ballistic-resistant helmets and more particularly to a lightweight titanium-based helmet shell.
2. Description of the Related Art
There is an ever increasing demand for lighter, more protective and affordable ballistic-resistant helmets.
Existing helmets are made of either heavy metals, such as steel, non-metallic, composites, or a combination of both, and often fall short of defeating new advanced small arms threats such as a 7.62 mm ball with a muzzle velocity in the range of 1500 to 2836 feet per second (fps). More specifically, ground troop, steel helmets weighing 2.5 lbs. of 0.033-inch thick steel, fabricated per Military Standard MIL-H-1988G, are required to have a V.sub.p 50 ballistic limit of only 900 feet per second. If existing state-of-the-art helmet wall thicknesses were increased, in order to meet a current challenge, (i.e., in the ballistic velocity range of 1500 to 2836 fps, noted above) their associated specific weights and/or minimum thicknesses become unduly excessive, a fact which results in user discomfort and could lead to possible rejection or abandonment during critical field operations.
U.S. Pat. No. 5,035,952, issued to P. Bruinink et al., discloses a ballistic structure comprising the solid combination of the metal first layer and a second layer consisting of a composite fiber material containing fibers with the tensile strength of at least 2 GPa and a modulus of at least 20 GPa, based on polyethylene with a weight average molecular weight of at least 4.times.10.sup.5 and a thermoplastic binding agent. A binding layer is applied between the first layer and the second layer, which binding layer contains the modified polyolefin. The first layer may consist of a metal or metal alloy such as steel, aluminum, or titanium.
U.S. Pat. No. 3,871,026, issued to E. Dorre, discloses a steel helmet, which is strengthened by coating its outer, generally convex face with a layer of ceramic particles deposited on the steel at a temperature above their sintering temperature, as by flame spraying or plasma spraying, if the ceramic material has a hardness value of at least 8 on the MOHS scale.
U.S. Pat. No. 3,774,430, issued to W. D. Greer et al. discloses a deep drawing technique for sheet metal into concave-convex forms. The sheet of material is placed over a die cavity. A ram made of malleable material, such as lead, forces the sheet into the cavity. The force of the ram, progressing inwardly from the edges of the sheet toward the center of the cavity, moves the sheet downward and inward into the cavity without appreciable change in the thickness of the material at any point. The sheet may thus be worked in cold condition, either in one or a succession of steps, without requiring heat treatment.
The following patents were also revealed in a patent search:
U.S. Pat. No. 5,376,426, issued to G. A. Harpell et al., entitled "Penetration and Blast Resistant Composites and Articles"; U.S. Pat. No. 3,859,399, issued to W. O. Bailey et al., entitled "Dense Composite Ceramic Bodies and Method for Their Production"; U.S. Pat. No. 4,090,011, issued to E. F. Barkman et al., entitled "Armor"; and, U.S. Pat. No. 5,480,706, issued to H. L. Lo et al., entitled "Fire Resistant Ballistic Resistant Composite Armor".
None of the aforementioned references discloses an effective technique for providing a deep draw for titanium-based materials, which can be utilized for the manufacture of helmet shells.